1. Field of the Invention
The present invention relates to endotracheal devices and the use of such devices in the intubation of a patient.
2. Brief Description of the Prior Art
During surgery and other medical procedures it is often necessary to insert an endotracheal tube (“ET”) into the trachea of a patient for the purposes of ventilation assistance, or otherwise. It is sometimes necessary, such as in emergency situations of cardiac arrest, acute respiratory failure or airway obstruction etc, to position an ET rapidly. Failure to properly position an ET, or failure to insert an ET quickly, can result in severe medical complication or even death.
For example, in an emergency cesarean section occasioned by fetus distress or other reasons, emergency placement of an ET in a mother's trachea is often required for general anesthesia. Failure to perform a rapid intubation after induction of general anesthesia may lead to severe damage.
There are numerous ways to intubate a trachea, the choice of which depends on the preference of the medical personnel and the anatomy of the patient's airway. For a patient of an expected normal airway, most anesthesiologists chose to intubate a patient after induction of unconsciousness and use of muscle relaxants. The glottis of a patient can be viewed under the direct laryngoscopy. Four grades of view of the glottis have been classified (Cormack, R. S. and Lehane J., “Difficult tracheal intubation in obstetrics,” Anesthesia 1984; 39: 1005-1111): Grade I, full view of the glottis; Grade II, posterior portion of the glottis is visible; Grade III, only tip of the epiglottis is visible; Grade IV, only soft palate is visible.
It is usually easy and possible to intubate a trachea with Grade I or II view, but it is often difficult or impossible to intubate trachea with Grade III or IV view rapidly when employing only direct laryngoscopy to assist in the intubation. It is not uncommon that an expected normal airway may turn out to be a Grade III or IV view of the glottis after paralyzing a patient and inspecting the airway using direct laryngoscopy. Furthermore, it is sometimes not possible to either ventilate a patient with a facial mask and or to intubate the patient (so called “non-intubation and non-ventilation airway emergency”). Therefore, in such situation it may prove lifesaving that proper oxygenation is maintained before intubation, and that intubation is accomplished as quickly as possible.
Compared to conventional mechanical ventilation (“CVM”), high frequency jet ventilation (HFJV) is characterized by its opening system, low tidal volume and low airway pressure. It is almost impossible to perform CMV before tracheal intubation in the situation described above, because it requires a close breathing circuit for positive pressure ventilation. However, it is possible to perform jet ventilation using a jet catheter before tracheal intubation, thus maintaining effective oxygenation and/or ventilation during intubation, which in turn, can prolong the time allotted for intubation in patients with Grade view III or IV and increase the safety of intubation.
In the case of an airway for which intubation is expected to be difficult, a fiber-optic guide device is frequently employed. However, such fiber-optic devices are usually used when the patient is awake, and not under general anesthesia. As currently practiced, fiber-optic assisted intubation does not provide sufficient oxygenation and/or ventilation before intubation. On the other hand, it is often difficult to intubate quickly enough a patient who is not breathing spontaneously using fiber-optic guided intubation to avoid worsening the patent's oxygenation, even at the hands of experienced medical personnel. Other shortcomings of fiber-optic assisted intubation include the fact that the glass fibers have a tendency to break after use, and the fiber optic lens can become dislocated and are expensive to replace. In addition, quite often secretions and blood in the airway can totally obscure the visual field. Therefore, in the situation of an unexpectedly difficult airway, it is impractical to do an emergency fiber-optic guided intubation.
Laryngeal mask airway (“LMA”) is used as a back-up airway management technique for unexpectedly difficult airways in most situations. However, LMA can not be used for long-term positive pressure ventilation or to protect the airway from aspiration. These drawbacks will limit its use in many emergency situations, such as during cardiopulmonary resuscitation, in a patient with a full stomach, and in acute respiratory failure, etc. Ultimately, LMA has to be changed to a trachea intubation with an ET for effective positive pressure ventilation.
Transtracheal jet ventilation has been recommended by the American Society of Anesthesiologist (ASA) in emergency situations of “cannot intubate, cannot ventilate” as a rescue method. This requires a percutaneous puncture of large bore (>G14) catheter into trachea and is quite invasive to patient. Often, anesthesiologists are not well trained to use transtracheal jet ventilation because of lack of practice in non-emergency situations where the method is infrequently employed because of its invasiveness and possible complications. Meanwhile, the lack of expiratory pathway for the jet pulse in the obstructed upper airway may increase the likelihood of barotraumas.
An audio-guided intubation stylet has been designed to guide tracheal intubation (U.S. Pat. No. 6,164,277). However, spontaneous breathing must be maintained to guide the ET. In the most situations, medical personnel prefer to intubate a patient after induction of general anesthesia and muscle relaxation. Under these circumstances, patients do not experience the discomfort otherwise associated with intubation, and less time is required to accomplish the intubation than when the patient is awake.
Another endotracheal assembly (U.S. Pat. No. 4,488,548) has been designed to prevent the whip effect of an insufflation catheter inside endotracheal tube and/or trachea, and to maximize air entrance during jet ventilation. In this case, the ET has spacers adjacent the distal end to space the insufflation catheter from the inner side walls of the tube. However, the insufflation catheter is not designed as a guide for intubation, and the distal end of insufflation catheter is well positioned as a guide into trachea.
An endotracheal assembly has been designed with the jet nozzles inside the ET (U.S. Pat. No. 4,270,530) to reduce turbulent during HFJV at a frequency above 600/min. Two jet nozzles spaced from each other inside ET are connected to separate feed lines. Although this arrangement permits selective ventilation of the lungs by gas currents adapted to the existing resistance conditions, it is not suitable to be utilized as a guiding catheter for intubation.
Christopher (U.S. Pat. No. 6,568,388) discloses a method and apparatus for guiding insertion of an endotracheal tube into a patient's trachea while continuing to supply air/oxygen in the patient's airway and lungs. The shortcoming of this design is that the intubation guide has a fixed angle on the distal end, thus it is unable to be adapted to the different view of glottis efficiently and quickly (e.g. a throat of Grade III may be higher than in Grade II). This makes it difficult to view the glottis with the fiber-optic device quickly in emergency situation. In addition, it will be difficult for the distal end of oxygen supplying catheter directly facing the vocal cord opening to provide adequate oxygenation and ventilation, while at the same time to adjust the distal end of the fiber-optic device for a good view of the glottis.
Huang (U.S. Pat. No. 5,445,161) discloses an apparatus and method for accurately securing an airway for the purpose of endotracheal intubation of a patient using a computed capnogram. The major shortcoming of this design is that the patient must have spontaneous breathing in order to use the capnogram as a guiding device. Patients are usually paralyzed with muscle relaxant to achieve maximum exposure of the glottis for intubation, and thus such patients are likely to develop apnea, especially in situations of securing an airway in an emergency. No methods of oxygenation and ventilation were designed for this apparatus in case of a patient's apnea, and thus the device is impractical for use in emergency situations.
McGrail (U.S. Pat. No. 4,584,998) discloses a multi-purpose tracheal tube, which can be used for high frequency ventilation, irrigation of airway and monitoring, and having three lumens provided in the tracheal tube. A major shortcoming of this design is that the opening of “insufflation lumen” is more than 5 cm away from the distal tip of tracheal tube, and the opening face the lumen, instead of pointing to the front. Thus, it would be difficult to use this “insufflation lumen” for generating powerful forwarding jet pulses for efficient oxygenation and ventilation if patients have apnea after receiving muscle relaxants. No PetCO2 monitoring catheter or other kind catheters are provided to guide and assist tracheal inbutation blindly in a difficult airway. The device appears to be useful for cleaning airway secretion during mechanical ventilation without interruption of oxygenation and ventilation, but does not appear to be adequate for assisting intubation in paralyzing patients with difficult airway.
In sum, there is a continuing need for an intubation device and method that can be employed to intubate patients quickly and reliably, especially in unexpected emergency situations in which conventional intubation techniques cannot be employed. It is very important that some kind of oxygenation and/or ventilation be maintained during intubation so that the chance of hypoxia and hypercapnia is minimized and the allotted time for intubation be prolonged.